The present invention relates to an electronic flash apparatus, and more particularly, to such an apparatus capable of providing an increased amount of flashlight emission and applicable to a flash photography of a camera or the like.
As is well known, a conventional electronic flash apparatus applicable to a flash photography and capable of providing an increased amount of flashlight emission (the degree of 40 to 50 in a guide number), as shown in FIGS. 1 and 2, is provided with a flashlight projector 10 the essential parts of which are a reflecting shade 2 which is formed of a curved plate perpendicular to the paper surface and is located opposite to a light emission window 1a of a flash body 1 and a flash discharge tube 3 disposed within the shade 2. The shade 2, as shown in FIG. 3, has a paraboloid portion 2a which is formed at the rear thereof and an ellipsoid portion 2b which is formed at an opening 2c adjacent to the paraboloid portion 2a. The discharge tube 3 is disposed at the focal point of the paraboloid portion 2a in a parallel relationship therewith. The opening 2c is covered with a transparent window plate 4. A main capacitor 5 and a circuit substrate 6 including a booster circuit 6a are adjacently arranged behind the light projector 10. The flash body 1 has a grip 7 which depends downwardly from the bottom of the body 1.
In a conventional electronic flash apparatus of a construction described above, among flashlight rays from the discharge tube 3, light rays reflected by the paraboloid portion 2a are projected forwardly as shown as light rays 3a to 3e in a parallel relationship with the radiation center line 3c of the discharge tube 3 and light rays reflected by the ellipsoid portion 2b are projected forwardly as shown as light rays 3f and 3g in the directions approaching a light axis 3c. An irradiation angle .alpha. of the projector 10 is defined by both groups of light rays 3h and 3k which are directly directed toward the upper and lower opening edges of the opening 2c without being reflected by the shade 2.
However, the flashlight source of the discharge tube 3 is practically not a point but is a pipe of a definite diameter (nearly 3 mm) and hence it is difficult to determine the irradiation angle .alpha. theoretically. Accordingly, the theoretical irradiation angle .alpha. is presently defined by modifying the shape for the most part of ellipsoid portion 2b adjacent to the opening 2c of shade 2 with the method of trial and error. Additionally, the shade 2 of the construction described above is most suitable for a shape to most effectively irradiate light from the tube 3 toward an object being photographed, which has the irradiation angle .alpha. of a substantially fixed value of 55.degree. to 60.degree.. Accordingly, an electronic flash apparatus capable of providing an increased amount of flashlight emission such as a guide number of the degree of 40 to 50 has the light projector 10 of an extremely large depth, therefore the apparatus itself becoming large in depth and thus disadvantageously degrading the convenience of portable use and ease of operation of the electronic flash.
In addition, in the conventional electronic flash apparatus, since main capacitor 5 and circuit substrate 6 including booster circuit 6a are adjacently arranged, the depth of flash body 1 is further increased, resulting in that the convenience of portable use and ease of operation of the electronic flash are further degraded.